[P2641R4](https://wg21.link/P2641R4)
This new builtin function is declared `consteval`. Support for
`-fexperimental-new-constant-interpreter` will be added in a later
patch.
---------
Co-authored-by: cor3ntin <corentinjabot@gmail.com>
The new constant interpreter's `clang::interp::InterpState` contains
both `clang::interp::Context` and `clang::ASTContext`. So using `S.Ctx`
and `S.getCtx()` was a bit confusing. This PR rename `getCtx()` to
`getASTContext` to make things more clearer.
Signed-off-by: yronglin <yronglin777@gmail.com>
